Variable-voltage transformer.



No. 894,714. PATENTED JULY 28, 1908. M. G. YOUNG.

VARIABLE VOLTAGE TRAQTSFORMER.

.APPLIOATION FILED mo. 26, 1907.

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UNITED STATES PAT T oFFroE.

MERCER G. YOUNG, OF PITTSFIELD, MASSACHUSETTS, ASSIGXOR TO GENERAL ELECTRIC,

I COMPANY, A CORPORATION OF NEW YORK.

VARIABLE-VOLTAGE TRANSFORMER.

Specification ofLetters Patent.

Patented Jilly as, 1908.

7 Application filed December 26, 1907. Serial No. 408,052.

tion.

My invention relates to variable-voltagetransformers' and especially to that class of transformers known as flux-shunt transformers, in which theamount of magnetic flux threading the secondary winding is made to vary by moving a magnetic core or cores,

More particularly, my invention relates to that class of fink-shunt transformers wherein a portion of a magnetic core is surrounded by the primary winding, and in which the secondary winding surrounds the portion of, the

core surrounded by the primary winding and a'second portion of the core not surrounded by the primary"winding. There is also a third portion ol'thc core not surrounded by ,either winding, and the-movable magnetic shunt or shunts are so arranged that the flux due to the primary winding may be assed through the secondary winding in on y one direction, and hence induce a maximum voltage; or may passth rough the secondary windings in two directions and induce a zero A transformer of this type is shown in Patent No. 865,985.

()nc object of my invention is to decrease the reactant-e in the secondary winding of such a trans'lbrnier, and more particularly when the secondary winding is'delivcring its maximum possible voltage. I thus lmprove the operation. of these transi'ormers, and do reference to the accompanying drawings, in

which I I Figure l is a somewhat diagrainmatical side elevation. of my invention, the coils ;be-

ing shown in section; Fig. 2 is a top view of" the smile; and Fig. 3 is an end view/Lon a smaller scale of the variable-reactance' coil.

eierring to Fig.- I, 1 shows a" magnetic core formed in the usual Fashion, with three legs (1 I) and c, which are magnetically joined.

and "11 are movable cores of magnetic maat one end by an end member d. surrounding the central leg I) is shown a primary winding 2, and surrounding the central leg and the left-hand leg (ris shown a secondary winding 3; Leads 2 and 3, attached, rean spectively, to the primary and secondary windin s, are shown in the usual fashion. These-earls may Lonnected in the well known way to a source of energy and to suitable translating devices. 4 is an independ. e5

'ent coil surrounding lega of the core, and

inclosed. within secondary winding 3. This 1 is connected by leads 6 to two coils 7 and 7,

.which are connected'in series (Fig. 2.). 7 and 7 are hollow, and Within the central Coils' to portions are the legs of two U-shaped'cores 8 and 9 of magnetic material. Core 8 is fixed; core 9 is movable in a vertical direction, as is shown in Fig. 1, in one limiting osition, with substantially neither of its egs' inclosed by coils7 and 7, and as shown in Fig. 3, in its other limitin position forming with core 8 asubstantial y closed magnetic circuit threading coils7 and 7. 10

3C terial. I have shown core 10 attached to a cord 12, which passes over a pulley 13, overv suitable means, such as a pin 16. 1 have shown a driving handle 17 suitably attached to )ulley 13, so that upon its movement it will cause pulley 13 to revolve and raise and lower cores, 1t), 11 and 9. Pulleys 13 and 14 may be held in anywell known fashion, and are so proportioned and placed that the movablecores may have a vertical movement, and may readily move. up and don/11 between legsa and b, and b and c, and inside of coils 7 and 7.- i

It will be obvious that while I have de-. scribed a certain method of attachingand moving the movable cores, many other methods may be'used, which will be equally as good; the only essential feature of'the movement used being that when core 10 is in its highest position, cores 11 and 9 shall beiirtlieir lowestposition, and thatthe upward when core 10 moves downward, and

"that when cores"1() and 9 are inthe other limiting position from that shown in Fig.

1,.that is, core is in a position similar to l current induced in the winding %i will, hence,

that in which core 11 is shown, and core 9 is in the position shown in Fig. 3, core 11 shall be in a position similar to core 10.

Fig. 2 shpws somewhat more clearly the arrangement of the windings u on the cores, and shows, as previously stater two reactive coils 7 and 7 connected in series. It will be obvious, however, that if so desired only one a construction of the reactive coils and the core which Iprefer; core-9 being shown in the position Which gives a maximum reactance in the coil.

The operation of the transformer is as fol lows: In the position of the moving cores shown in Fig. 1, the flux due to the primary winding passes around. the closed magnetic ciruci't formed by leg 1), core 1]., leg 0, and end member d The secondary'winding 3 will then have induced init its maximum voltage. When the positions of cores I0 and 11 are reversed,that is, core 1] is drawn up and away from legs Z) and c, and core 10 substantially fills the air-space between legs a and b, above the winding, the magnetic flux induced by the primary winding will pass through the closed magnetic circuit leg- I), core 10, leg at and end member (1. Secondary winding 3 will then be cut by two substan= tially equal and opposing fluxes, and no voltage will be induced in it, if there is no magnetic leakage. In the position shown in Fig. 1,-if coil 4 were absent or open-circuited, the

.reactive voltage in secondary winding 3 would be very great, and there would be an excessive impedance. This excessive impedance is due to the fact thatthe area of the path for the reacrive flux is comparatively large and has included within it leg a, which is encircled solely by the secondary winding 3, winding 4 being for the moment not con sidercd. This react anceis so great that, unless means are takento reduce it, a large transformer of this type is ractically inoperative'. The means where y I reduce this reactance .is by the independent auxiliary winding 4 surrounding leg a-alone, inside of the secondary winding 3 and connected to .a coil or. coils of variable reactance. The action of this independent coil is as follows: In the position of the cores shown in Fig. 1, 11 is in the position for maximum voltage and maximum load. The reactive flux due to l he secomlary winding 3 induces in the auxiliary winding 4 a voltage, and hence a current is produced in winding 4, lead 6, and coils 7 and 7. The variable reactive coils 7 and 7 have the minimum reactance, as core .3 is in a position away from the coils. The

be a maximum, and the reaction ol the flux produced by this coil will greatly increase the reluctance of the leakage path for the reactive fillXill winding 3, and hence will decrease the total reactive voltage. In the limiting position,'reverse to that shown in Fig. 1,- that is, with core 11. raised the full amount and core-1O lowered the full amount, a minimum voltage willbe induced in the secondary winding 3. At the same time, core 9 is raised to its full extent, and the rcactance of the variable reactive coils 7 and 7 is a maximum. Thus, the current in the auxiliary independent coil 4 and the reactive coils 7 and 7" will be a minimum, and the losses from this source will be reduced. It will be obvious that for intermediate positions of the cores phenomena intermediate to those described will occur.

I do not desire to limit myself to the particular construction and arrangement of parts which I have shown and described, since changes, which do not depart from the spirit of my'invention, and which are within the scope of the present claims, will be obvious to those skilled in the art. I

What I claim as new and desire to secure by Letters Patent of the United States, is,-

1. The combination, in a variable-voltage transformer having primary and secondary windings, and means for varying the flux due to the primary winding passing through the secondary winding, of means for decreasing the reactance of the secondary winding.

2. The combination, in a variable-voltage transformer having primary and secondary windings, and means for varying the flux due to the primary winding passing through the secondary winding, of an independent coil of variable reactancein inductive relation to the secondary winding.

3. The combination, in a variable-voltage transformer having primary and secondary windings and means for varying the flux due to the primary winding passing through the secondary winding, of an independent coil in inductive relation to the secondary winding and short-circuitcd'through acoil of .variable reactance. 1

4. The combination, ina variable-voltage transformer having a three-legged core, a primary winding surrounding one leg, a secondary winding surrounding both the leg carrying the primary winding and a second ,leg, and means for sending the tlux due to the primary winding through the other two legs alternately, of means for reducing the reactive voltage in the'secondary winding. 5. The combination, in a variable-voltage transformer having a three-legged core, a primary winding surrounding one leg, a secondary. winding surrounding both the leg carrying the primary winding and a second leg, and means f r sending the llux due to the primary winding through the other two legs alternately, of an independent coil surrounding the leg surrounded by the secondary winding but not surrounded by the pri- -mary winding, and short-circuited through a second coil whose reactance may be varied. 6. The combination, in a variable-voltage transformer having a three-legged core, a

primary winding surrounding one leg, a sectransformer having a threelegged core, a

primary winding surrounding one leg, a secondary winding surrounding both the leg carrying the primary winding and a second leg, and two movable magnetic cores, one

causing the magnetic flux induced by the primary winding to thread the secondary Winding in a single direction, the other causing the magnetic flux induced by the primary winding to thread the secondary winding in two opposite directions, and anindependentcoil surrounding the leg surrounded by the secondary winding but not surrounded by the primary winding, and short-circuited through a coil with a magnetic core partly movable, the movable portion producing its greatest effect for a maximum induced voltage in the secondary udnding.

8. The combination, in a variable-voltage transformer, of .a three-legged core, a' pri mary winding surrounding one leg of said core, a secondary winding surrounding both the leg surrounded by the primary winding and a second leg, an independent coil wi in the secondary winding surrounding the leg not surrounded by the prin'rary winding, and connected to two other windings in series mounted in a separate core, a portion of which is movable, two movable cores sliding within the legs of the first core, and means for moving these cores in an opposite direction and for simultaneously moving the movable portion of the core surrounded by the auxiliary coils-so as to produce a minimum reactance in these coils when the secondary winding has induced in it a maximum voltage, and for producing a maximum reactance in these coils when the secondary windings has induced in it a minimum voltage.

In witness whereof, I have hereunto set my hand this seventeenth day of December, 1907.

, MELTEE G. YOUNG Witnesses:

GEORGE L. Mownn WILLIS A. Isunnn. 

